Why is 440 hz concert pitch

A is the musical pitch corresponding to an audio frequency of Hz, which serves as a tuning standard for the musical note of A above middle C, or A4. 9 Sep A or A4 (also known as the Stuttgart pitch), which has a frequency of Hz, is the musical note of A above middle C and serves as a. Hz is the standard accepted pitch reference for tuning musical A is commonly used as the concert pitch in the UK and the US.